Recent advances in cable and satellite distribution of subscription and “on-demand” audio, video and other content to subscribers have given rise to a growing number of digital set-top boxes (sometimes referred to as Digital Consumer Terminals or “DCTs”) for decoding and delivering digitally broadcast programming. These boxes often include additional circuitry to make them compatible with older analog encoding schemes for audio/video distribution. As the market for digital multimedia content of this type grows and matures, there is a corresponding growth of demand for new, more advanced features.
Content owners are concerned about protecting their content when in digital form. Digital copies of content preserve their quality through subsequent copying, unlike analog copies. Digital content is available through terrestrial broadcast, digital cable, satellite, and the Internet. In some cases, the digital content is protected during transport, but in other times it is not. For example, digital cable uses conditional access technology to protect video programs during transport, but terrestrial broadcast television has no encryption of the video programs.
A natural extension of on-demand programming is a personal video/audio recorder (PVR) capability whereby desired programming (e.g., a “broadcast” movie, program, audio recording, etc.) can be recorded to a storage medium (e.g., HDD) and played back later.
However, the potential unauthorized copying of stored content poses a significant problem for content providers and MSO's (Multiple Service Operators). Since the programs stored on a PVR may be considered to be valuable, it is desirable to protect the content on the disk from unauthorized access, either by the subscriber or by others who might come into possession of the set-top box. To overcome this problem the programs are often stored on the storage medium in an encrypted form using a private encryption key that is unique to each and every set top box. The private encryption key is often stored in a secure hardware portion of the set top box so that it is available to encrypt and decrypt the stored programs. Unfortunately, one problem with this approach is that if the set top box should fail so that the private encryption key is not able to be accessed, the programs stored in the storage medium cannot be decrypted even though the storage medium itself may be intact and the data otherwise accessible. Another problem with this approach is that it prevents a storage medium that is used to record programs with one set top box from being used with another set top box to play back or render the programs. This effectively limits the portability of the storage medium, which is a particularly noteworthy limitation when the storage medium is an external storage medium that is generally intended to be used with a variety of different rendering devices. For instance, a hard disk drive (HDD) may be connected to the set top box via an I/O interface (e.g. SATA) on the set top box. The HDD may be easily detached from the set top box by the user without opening the set top box enclosure and, likewise, easily attached to a second set top box.
Accordingly, it would be desirable to provide a method and apparatus for encrypting programs recorded by a set top box on a storage medium in an encrypted format so that they can only be accessed by authorized users, but which still allows the authorized users to access the programs using different set top boxes. Furthermore, it would also be desirable if the method and apparatus allowed an MSO to remove an internal storage medium (i.e. a storage medium physically mounted within the enclosure of the set top box) containing encrypted programs from a non-operational set top box and install it in a new set top box so that the new set top box allows the authorized users to access the programs from the new set top box.